Organisms are characterized into two broad categories based upon how they obtain their energy and nutrients: autotrophs and heterotrophs. Autotrophs are known as producers because they are able to make their own food from raw materials and energy. Examples include plants, algae, and some types of bacteria. Heterotrophs are known as consumers because they consume producers or other consumers. Dogs, birds, fish, and humans are all examples of heterotrophs. (Information from Britannica)
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